Optical amplifying arrangement using carbon nanotubes

ABSTRACT

A method of using a carbon nanotube assembly comprising: arranging a signal responsive array of nanotubes on a substrate, and heterodyning a signal processed by the array of nanotubes on the substrate.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a DIV of Ser. No. 10/789,390, filed Feb. 27, 2004now U.S. Pat. No. 7,099,071 which is a DIV of Ser. No. 10,646,945,(filed Aug. 22, 2003) now U.S. Pat. No. 7,205,021, which is a DIV ofSer. No. 09/901,309, (filed Jul. 9, 2001), now U.S. Pat. No. 6,700,550,which is a DIV of Ser. No. 09/523,626 (filed Mar. 13, 2000), now U.S.Pat. No. 6,258,401, which is a DIV of Ser. No. 08/988,801 (filed Dec.11, 1997), now U.S. Pat. No. 6,038,060, which claims benefit of Prov.Applic. 60/036,085 filed Jan. 16, 1997, all incorporated herein byreference.

This is based on U.S. provisional patent application by Robert J.Crowley, Ser. No. 60/036,085, filed on Jan. 16, 1997.

TECHNICAL FIELD

This invention relates to small aligned conductors and junctionsconfigured to efficiently admit, modify and emit electromagneticradiation around light wavelengths.

BACKGROUND INFORMATION

Optical materials employing microstructures that exhibit the property ofbirefringence are commonly used to generate harmonic energy around lightwavelengths. These materials are useful for frequency doubling, triplingor multiplying one or more fundamental inputs. Layered crystalstructures are known to exhibit practical nonlinear transmission oflight energy that usually result in harmonic generation withefficiencies that are generally low. Attempts have been made to optimizethe harmonic generating efficiency of various materials by orientingmolecules sandwiched between substrate materials. In U.S. Pat. No.5,589,235, an applied magnetic field is used to pre-align molecules, andthen a source of radiation is used to cross-link the molecules so thatthey maintain their position after the magnetic field is removed. Inanother attempt to fabricate a device that exhibits high harmonicgenerating efficiency, U.S. Pat. No. 5,380,410 describes a method bywhich periodic electrodes may be fabricated to provide inversion regionsthat improve the efficiency of a ferroelectric material which exhibitsan intrinsic nonlinear optical property. The fabrication of a nonlinearoptical region or layer on a material that generally has inherentlylinear characteristics is disclosed in U.S. Pat. No. 5,157,674 whichteaches a process by which a charge transfer dopant is introduced toproduce a semiconducting region on a bulk glass or microcrystallinesubstrate.

One apparent drawback to these approaches is wavelength-dependentattenuation. This attenuation occurs when lightwave energy propagatesthrough lossy materials, resulting in attenuation. In general, bothpolymer and glass substrate materials exhibit high attenuation throughabsorption in the near UV and UV regions. Microcrystalline materialsthat utilize birefringence generally must have sufficient light pathpropagation length to produce sufficient phase changes for significantharmonic generation. Longer path lengths usually result in even greaterattenuation.

Researchers have had to resort to modification of bulk materials ororientation of molecules in a solution or matrix to produce structuresthat exhibit optical nonlinearity, and usable harmonic generation. Theseresearchers have not been able to successfully utilize practices thatare now common in the electromagnetic radio electronics fields, eventhough light waves are merely electromagnetic waves of shortwavelengths, primarily because techniques and materials for thefabrication of practical electromagnetically responsive elements in thesmall sizes necessary for efficient use at light wavelengths in theranges of 10,000 nanometers and shorter are not available. Opticalcrystal materials and composite materials, due to their structure, makeit difficult to optimize the orientation of individualelectromagnetically responsive elements.

An important aspect of successful fabrication and use of radio frequencynonlinear harmonic generating materials is the ability to control theorientation and sizes of those elements with respect to variouselectromagnetic fields. This is possible since radio frequency waves,and even microwaves, are relatively long. Developers of nonlinear,harmonic-producing devices for radio wave applications have been able tosuccessfully fabricate numerous circuits, cavities, transmission lines,junctions and other structures scaled to radio wavelengths. Thispractice has been extended over time to include VHF, UHF, microwave andso-called millimeter wave regimes, and has included discrete components,transmission lines and antenna systems that have been scaled down tooperate optimally at ever-higher frequencies.

Designers have also been able to fabricate nonlinear junctions that aresmall with respect to the wavelengths involved. These junctions arecapable of rectification, mixing, detection and amplification over aportion of the full cycle of the alternating current, electromagneticwave energy, and include conventional diodes, Shottky diodes, tunneldiodes, transistors, field effect transistors, bipolar transistorsincluding discrete components and mass array fabricated devices such asintegrated circuits and linear and two-dimensional arrays.

It would be logical to extend this practice into infrared, lightwave andultraviolet regimes if the materials, designs, and techniques needed toaccomplish these developments could be understood and executed. Worktoward this goal is proceeding today with limited success. It has beensuggested that carbon nanotubes, also known as C₆₀ or fullerenestructures, could be used as part of such electronic devices that wouldoperate efficiently in the optical domain. Researchers have had limitedsuccess with films of C₆₀ that have appeared to have properties that areboth electronic and optical, and initial attempts at producingcomponents have been made using layered, deposited and more-or-lessrandom length coatings of this and other polymeric conductive materials,but efficiencies, though improved, are still not optimized, and designcriteria for practical devices are still not developed.

It would be desirable if junctions, elements and conductors could befabricated that operate in the regime of light wavelengths in a way thatmade them efficient, repeatable and manufacturable. It would bedesirable if these junctions, elements or conductors were configurableto provide efficient nonlinear transfer characteristics that could beused for generating harmonics, mixing, modulation, frequencymultiplication, and amplification of lightwave signals in addition tomore linear antenna-like properties such as resonance, charge storageand reradiation of electromagnetic field energy. Many usefulapplications would be found for the successful highly efficientnonlinear optical material, device or technique that could convertinfrared energy to visible lightwave energy and to ultraviolet lightwaveenergy in an efficient manner. It would be particularly desirable if thedevices could be produced quickly and inexpensively, and if theircharacteristics could be controlled effectively using knownmanufacturing process control techniques.

SUMMARY OF THE INVENTION

The invention features a light responsive electromagnetic conductorplaced in electrical contact with a junction exhibiting polar, nonlinearelectrical transfer characteristics. The invention allows conversion ofradiant light frequency energy to a conducted electron charge transferacross a semiconducting junction, and subsequent conversion andreradiation of a portion of the energy to lightwave energy at a multipleof the light frequency. In one aspect, a method of generating harmonicenergy near light wavelengths is described comprising the steps ofexposing a conductor to an infrared, visible or ultravioletelectromagnetic light energy having an alternating waveform, inducing acurrent with electromagnetic energy in the conductor to cause anelectrical charge to cross a junction, and emitting at least a portionof the energy at a harmonic multiple of the light energy.

In one aspect, the invention relates to the use of a substrate materialto support carbon nanotubes which are used as frequency selectiveelectrical conductors. In one embodiment, the conductors are polarizedwith respect to the substrate. In another embodiment, a foraminoussubstrate is used to influence and support the orientation of theelectrical conductors. In another embodiment, the foraminous substratesupports a nanoparticle which creates at least a portion of a nonlinearelectrical junction. In another aspect, the invention relates to aconductive element with a non-linear charge transfer region that issmall with respect to that element.

In one aspect, the invention relates to an antenna structure that admitsand radiates at light wavelengths. In another aspect, a lightwaveelectromagnetic antenna having a linear conductor is attached to asubstrate material, with the linear conductor having an electricallength sized to respond to an electromagnetic light wavelength. Inanother aspect, the invention relates to antennas with conductingelements of less than 2000 nanometers in length that operate near lightwavelengths. In one embodiment, the conductors form a traveling wavestructure. In another embodiment, the conductors are arranged to form alog periodic structure.

In another aspect, the invention relates to a conductive element with anelectrical length about a multiple of ¼ wavelength of a lightwavelength. In one embodiment, the electrical length of the conductorinclusive of a junction may be about 600 nanometers corresponding to ½wavelength of infrared light. Impinging infrared light energy iscollected, rectified and reradiated at a multiple of the infrared lightfrequency with high efficiency. In another embodiment, the electricallengths of the conductor may be in a range from about 20 nanometers toabout 2000 nanometers corresponding to ultraviolet, visible and infraredlight. In one embodiment, the lengths of the conductors may be staggeredto form a broadband structure. In one embodiment, the conductors arearranged in a generally parallel relationship.

In another aspect, the invention relates to an array of conductiveelements with electrical lengths around a multiple of ¼ wavelength oflight, arranged so that at least one optical port and at least oneelectrical port, are held in communication via a nonlinear junction. Inone embodiment, the electrical port is a terminal on a optical devicewhich modifies a charge transfer characteristic of a junction. In oneembodiment, a device for rectifying an alternating waveform occurringaround light wavelengths is comprised of a short conductor of less than10,000 nanometers in length and a nonlinear region with an electricallength less than the light wavelength. In another embodiment, thenonlinear junction region consists of a nanoparticle. In anotherembodiment, the junction is a polarized, doped region with an electricallength shorter than ½ of the light wavelength.

In another aspect, the invention relates to the process by which thegrowth of lightwave antenna elements upon a substrate may be controlledby observation of an optical property. In one embodiment, variouslengths of nanotubes are grown in a controlled manner upon thesubstrate.

The foregoing and other objects, aspects, features, and advantages ofthe invention will become more apparent from the following descriptionand from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like reference characters generally refer to the sameparts throughout the different views. The drawings are not necessarilyto scale, emphasis being placed upon illustrating the principles of theinvention.

FIG. 1 is a side view of a prior art radio frequency dipole antenna witha center diode junction shown in relation to a signal generator and asignal receiver located in space around the antenna.

FIG. 1 a is a perspective view of a prior art radio frequency theftcontrol tag.

FIG. 2 is a cross-section of a foraminous substrate material structurewith nanoparticles.

FIG. 3 is a partial cross-section of a foraminous substrate materialwith nanoparticles and linear elements disposed at right angles to thesubstrate.

FIG.4 is a partial cross-section of a light modifying device witharranged linear elements of approximately equal lengths joined at asubstrate and a terminal attached to the substrate.

FIG. 4 a is a partial cross-section of a light modifying device in whichlinear elements are of various lengths along the length of a substratematerial.

FIG. 4 b is a partial cross-section of a light modifying device in whichlinear element lengths are tapered with respect to each other and asubstrate material.

FIG. 5 is a cross-section of a light modifying device in which thesubstrate with linear elements are disposed with respect to anelectrical terminal and two optical windows to form a 3 port system.

FIG. 5 a is a schematic diagram of the light modifying device of FIG. 5in which lightwave energy is admitted and transmitted after undergoingfrequency conversion, mixing or amplification.

DESCRIPTION

Referring to FIG. 1, a prior art radio frequency dipole antenna 1 isshown as it is used in many forms of radio communications and shownparticularly in this case for illustrating one common use and techniquefor harmonic generation and reradiation. Such antennas ordinarilycomprise two ¼ wave sections joined at or near the center and mayinclude a nonlinear diode junction 2 connected therebetween. It is knownthat a ½ wave antenna has desirable properties that efficiently pick upand radiates radio frequency energy, and therefore the so-called dipoleantenna is considered to be a basic building block in the antenna art.This desirable antenna property is generally known as resonance, and itshould be understood that there are other lengths of conductors thatexhibit resonant effects as a function of frequency and length. An alarmsystem for theft control purposes may be constructed with such anantenna and a transmitter 3 operating at frequency n, and a receiver 4,tuned to listen for signal(s) at frequency 2 n. When transmitted signaln impinges upon the antenna 1, a changing electrical field induces acurrent which travels through the length of that antenna. Ordinarilythat field would reverse in the case of linear operation (no diode) ofthe antenna elements, but in this case the presence of the nonlineardiode junction 2 partway through the element creates a conductancechange part way through the conduction cycle which limits and distortsthe ordinarily linear current flow and converts it into a nonlinear,non-sinusoidal waveform. Nonlinear waveforms contain harmonic energy andmay be described by transform equations which are based on Fourier'sTheory of Trigonometric Series which among other things show that allcomponents of a given waveform are comprised of at least one or moresinusoidal waveforms that are mathematically related. Some of theharmonic energy is reradiated into space and may be picked up by nearbyreceiver 4, which may then sound an alarm. A typical transmitted signalmay be 1000 MHz. In this case, the electrical length of the dipoleantenna may be one-half of the wave length of 1000 MHz, which in freespace is approximately 30 centimeters, resulting in a correspondinghalf-wave dipole structure of about 15 centimeters long.

Referring now to FIG. 1A, a prior art radio frequency theft control tagof which tag 5 is comprised of a thin conductor 6 and a small diode 7mounted within a flat plastic housing or substrate 8. The thin conductor6 may be a foil shaped to form one or more dipole antenna lengths inparallel which may be harmonically related as a function of electricallength, therefore the dipole antenna 1 previously shown in FIG. 1 may bemodified so that it reradiates even more efficiently at double the inputfrequency. A typical theft control tag system may operate at about 5000MHz, which corresponds to a wavelength of about 6 centimeters and acorresponding half-wave dipole length of about 3 centimeters. Thereforea transmitter may be placed that emits at 5000 MHz, and a receiver maybe placed that listens at 10,000 MHz, or twice the frequency. Thesefrequencies are just one example of a phenomenon that is observable atall electromagnetic wavelengths but that has not been put to use inlight wave regimes because materials could not be fabricated, nor has itbeen apparent that ordinary radio wave practices could be usefullyapplied in such a way to very short wavelengths such as those associatedwith light wavelengths.

Recently, large-scale synthesis of aligned carbon nanotubes has beendemonstrated at the Chinese Academy of Sciences in Beijing by Li, et al.These structures can be grown on a substrate of foraminous silica andhave lengths in the range of up to about 50 micrometers long. Carbonnanotubes are conductive structures with high length-to-diameter ratios,and it has been found that that these exhibit some nonlinear opticaleffects. It has been suggested that carbon nanotubes may be used fornumerous optical purposes but none in a way that utilize ordinary radiowave antenna techniques scaled to light wavelengths.

Referring now to FIG. 2, a foraminous substrate material structure withnanoparticles, substrate material 11 is comprised of silica, silicon orother material that may insulate or partially conduct and which may bemade foraminous in a controlled, predetermined manner. Depressions 13may extend partially into the substrate material or apertures 15 mayextend through the thickness of the substrate. The foraminous substratestructure may be made by leaching the silica with the sol-gel process(not shown) which produces mesoporous silica, and may alternatively beused to produce a controlled foraminous surface in silicon, which is asemiconductor, or gallium arsenide, for example. If the substratematerial 11 is of a dopable semiconducting material, doped region 17 maybe produced by processing known in conventional transistor materialfabrication practice. The doped region 17 may be effective to rendersome or all of the region on the substrate more or less polarized withrespect to electrical charge or current transport across that region.The region 17 may extend into depressions 13 or apertures 15. Ironnanoparticles 19 may be produced in the substrate by the method ofdepositing a finely ground iron oxide dust (not shown) in the poroussubstrate and then by reducing the iron oxide by heating the substrateto a temperature of about 550 degrees centigrade in 180 torr of flowingH₂N₂ for approximately 5 hours. The remaining reduced metal leaves theresidual nanoparticle 19 that may be embedded in the substrate. Thesubstrate itself should be thin. The thinnest substrates may be in arange of 200 nanometers or less and may be produced by tapering the edgeof a thin section of substrate material down to a near molecular edge byacid etching, drawing, or other ablative process. Alternatively, thinsections may be produced in thicker areas by ablative methods such asspark erosion or laser ablation, the advantage being that a strongersurrounding support structure may be formed around a very thin activearea of the substrate.

It is important to point out that oxides of metals such as iron arecommonly known to have semiconducting properties and therefore may formpart of a semiconducting junction. The small size of these particularnanoparticles makes them suitable for junctions that are electricallyshort enough to operate effectively at very high frequencies, includinglight frequencies since they are small relative to light wavelengths. Atypical red light wavelength may be around 600 nanometers, and an ironnanoparticle may be less than 100 nanometers and typically may be in therange of 10 to 30 nanometers average diameter.

Referring to FIG. 3, a prepared substrate 11 with embedded nanoparticles19 may be supplied with acetylene-fed carbon nanotubes 21 extending fromdepressions 13 or apertures 15. The mechanism of nanotube generation andgrowth in a prepared foraminous substance appears to involve a processin which particles act like seeds for the initiation of nanotube growth,and that the orientation and direction of the initiated nanotube growthis then influenced by the orientations of the depressions and apertures,which may simply serve as guides at the early stage of growth. Otherforces and influences such as a static electric field, a magnetic field,or the application of various electromagnetic fields such as radio waveenergy and lightwave energy, may also influence the orientation andgrowth process. In particular, the application of a static electricfield to the substrate and subsequent charging of the growing nanotubesmay improve separation and aid in the regularity and evenness of theseparation of individual strands through the mutual repulsion forceresulting from an adjacent like charge. The apparatus to grow nanotubesconsists of a chamber (not shown) into which acetylene is introduced andburned incompletely which creates soot. The soot is comprised ofregularly shaped carbon atoms which have been observed to self assembleinto the nanotube configuration.

Still referring to FIG. 3, the length L of the nanotube may becontrolled by regulating the time allowed for growth. The average lengthof the nanotube or nanotubes may be monitored by measuring the lightabsorption characteristics during the growth process which change as thetube grows. Generally, as the tube lengthens it admits longerwavelengths according to a relationship known in electromagnetic theoryin which the propagation time of the electric charge across a bodydetermines its electrical length and its admittance or ability topreferentially absorb and/or radiate at a specific wavelength. For a ½wavelength dipole arrangement each side of the substrate may have anapproximately ¼ wavelength long conductor, and is most responsive to awavefront that propagates in a direction that is perpendicular to thebroad side of the conductors. Conductor lengths L that correspond to ¼wavelength from ultraviolet, through the visible and to infrared lightmay have a range from about 60 nanometers to about 10000 nanometers maybe accomplished using current techniques. The axial relationship of thetwo ¼ wavelength conductor set 25 and their more-or-less perpendiculardisposition relative to the substrate make this array polarizationsensitive to lightwave energy. In general, a higher current and lowervoltage may be observed near the center of a resonant dipole arrangementin accordance with the conventional antenna art. It may be desirable toraise the voltage near the junction which may be accomplished either byadjusting the length of the antenna element or by placing the junctionoff center. It is known that ½ wavelength resonant antennas exhibitcurrent minima and voltage maxima at the ends of the conductors,therefore, it may be desirable to approach lengths of ½ wavelength oneach side of the substrate thereby producing a resonant structure aboutat about one full wavelength.

The thickness of the substrate and the thickness of the conductor mayresult in a longer charge transport pathway that tends to shorten theoverall length of the dipole antenna somewhat. This shortening effect iswell known in the radio art as it relates to thick antenna elements, butis less appreciated as it relates to the intersection of antennaelements since the delay times associated with radio frequencyconnections and intervening junctions are usually small with respect tothe wavelength involved. In lightwave regimes these delays are moresignificant. To reduce internal charge transport or propagation ofcharge delay in the invention, a paired junction 23 may be constructedby growing two opposing nanotubes from one iron particle with theadvantage of better electrical length control and less dependence uponsubstrate thickness to define the length of the structure.

It should be pointed out that the exact role and semiconductiveproperties of reduced metals within a substrate and their operation whenconnected to at least one end of a carbon nanotube has not been studiedin sufficient detail, and it is possible that any discontinuityrepresented by any interruption of the nanotube itself, includingtermination, distortion etc., may be found to have inherent nonlinearproperties which could additionally benefit the efficiency of thepresent invention. Due to the small size of these junctions and the highfrequencies involved, tunneling effects, in addition to band gapeffects, may be produced at or near the junctions or physicaldiscontinuities of the structures as generally described.

Referring now to FIG. 4, an optical antenna array 26 has pairedjunctions 23 and conductor sets 25 of approximately equal lengths joinedat substrate 11. Electrical terminal 27 is bonded to the substrate 11 bybond 29 which may be in electrical communication with either doped orundoped regions of the substrate. Application of a current to terminal27 is effective to bias the electrical transport properties of theassembly. Application of an alternating waveform is effective tomodulate the transport properties across the optical antenna array 26 ina periodic manner which causes it to act in a way that is similar to adiode switch or mixer arrangement as commonly encountered in theelectrical and radio art. Since the inherent transport properties acrossthe optical antenna array 26 are nonlinear, mixing and superimpositionof the modulating electrical waveform with the light waveform isproduced. Conversely, variations in the amplitude or phase of the lightwaveform are effective to influence the electrical port. These mayproduce sum and difference signals through the various processes knownas heterodyning and modulating, and may result in an amplification orincrease of the total power realized.

Referring to FIG. 4 a, the optical antenna array 26 is supplied withstaggered conductor sets 31 disposed upon substrate 11. As in the priorart radio frequency tag 5 shown in FIG 1 a, the lengths of the antennaor conductor elements are effective to enhance reradiation at certainwavelengths of operation. Referring once again to the light modifyingdevice assembly of FIG. 4 a, two, three or more wavelengths may beselectively admitted and radiated depending upon the mix anddistribution of element lengths. Best efficiency is obtained when theradiated energy is harmonically related to admitted energy. Practicaldevices with bandwidths broad enough to admit and radiate over a widerange of wavelengths are accommodated with this construction. To produceelements of varying lengths on the substrate, the process of particledeposition and nanotube growth may be repeated multiple times on asingle substrate since the material C₆₀ can withstand considerablethermal cycling without damage.

Referring to FIG. 4 b, an optical antenna array 26 is patterned after acommonly known antenna type known as a log-periodic dipole array.Tapered length conductor sets 25 are effective to operate over a widerange of wavelengths, and coupling of the electromagnetic fields betweenadjacent elements is effective to selectively reinforce wave propagationso that a directional preference of the optical antenna array 26 isobtained. The log-periodic dipole array is merely exemplary; otherantenna types include, but are not limited to, dipole, Yagi-Uda,collinear, phased array, rhombic or other structures that are known toradiate and admit electromagnetic energy in accordance with the antennaart, and conductors that are scaled and positioned with regard to thewavelengths of electromagnetic energy involved which may includetransmission line structures comprised of more or less linearconductors.

Referring now to FIG. 5, an optical antenna array device 42 encloses theoptical antenna array 26 which is mounted in a tubular holder 43 bymeans of a mounting plate 41. The holder may be made from machinedaluminum which may have an outside diameter of about 1 mm and an insidediameter of about 0.25 mm or less. Larger or smaller structures may beconstructed within the scope of the invention. A coating of aluminum 45is deposited in center bore of holder 43 by a vacuum metalizationprocess. The coating acts like a mirror which helps direct light fromwindow 53 to and from the optical antenna array 26. Electrical wire 47is brought out through insulator 49 to terminal 51 for the purpose ofattaching and electronic device such as art oscillator, a receiver, aspectrum analyzer, a pulse generator, an amplifier, a power supply orthe like to electrical terminal 27.

Referring to FIG. 5 a, the operation of the optical antenna array device42 is shown in block diagram form. Light source 61 (λ) shines light beam63 into holder 43 and onto mounting plate 41 carrying the opticalantenna array 26. The glancing angle of the light beam against theinside of the holder helps avoid a condition where all the light energywave front is entirely perpendicular to the plane of the substrate.Mounting plate 41 may alternatively be positioned diagonally in holder43 so that light energy propagates in a direction that is generallybroadside to the long axes of the carbon nanotubes 21, as shown in FIG.4, which are aligned with a generally perpendicular orientation withrespect to the substrate material 11.

Returning once again to FIG. 5 a, light beam 63 may interact withoptical antenna array 26 which may produce reflected beam 65 (λ/2) atleast a portion of which contains high levels of second, third or higherorder harmonic energy. Simultaneously, transmitted beam 67 (λ/2) mayinteract with optical antenna array 26 which generates significantharmonic energy and propagates in a direction generally opposite lightbeam 63. Some isolation is afforded by the light loss that occurs at theoptical antenna array 26 so that a plurality of light beams of differentwavelengths may be introduced simultaneously, and their products may bedetected at terminal 51. Polarization and isolation may be enhanced bythe use of polarizing filters (not shown) and magnetic rings (also notshown) attached to one or more ends of holder 43.

What has been described is a practical harmonic generating device thatcan operate over a wide range of light wavelengths utilizing an opticalantenna array system that is optimized for lightwave operation. The useof an array of elements that are produced at dimensions and oriented ina repeatable manner create optimal conditions for efficient collection,conversion and radiation of electromagnetic lightwave energy. This highefficiency is due to the ordered arrangement of conductive elementsoptimally dimensioned for electromagnetic radiation as previouslypracticed in the radio and antenna art which may now be practicallyapplied to optical wavelengths. Further, attenuation effects areminimized through the use of optical elements which may operate in freespace being attached at only one end, rather than in bulk, disorderedform or in a solution. The invention allows the fabrication andpractical use of linear conductors as antennas with lengths thatcorrespond to light wavelengths and therefore allows the application ofradiowave antenna, transmission and radiation practices, includingharmonic generation and mixing, detection and frequency multiplication,to the lightwave regime.

Variations, modifications, and other implementations of what isdescribed herein will occur to those of ordinary skill in the artwithout departing from the spirit and scope of the invention as claimed.Accordingly, the invention is to be defined not by the precedingillustrative description but instead by the spirit and scope of thefollowing claims.

1. A method of amplifying a signal with a carbon nanotube device,comprising: applying a first signal to said carbon nanotube device;applying a second signal to said carbon nanotube device; and outputtinga sum or product of said first signal and said second signal from saidcarbon nanotube device.
 2. The method of amplifying a signal with acarbon nanotube device, as recited in claim 1, wherein said carbonnanotube device comprises an array of carbon nanotubes.
 3. The method ofamplifying a signal from a carbon nanotube device as recited in claim 2,wherein at least one of said carbon nanotubes is attached to a junctionon a substrate.
 4. The method of amplifying a signal from a carbonnanotube device as recited in claim 3, wherein said junction comprises ametal.
 5. The method of amplifying a signal from a carbon nanotubedevice as recited in claim 3, wherein said junction comprises a metaloxide.
 6. The method of amplifying a signal from a carbon nanotubedevice as recited in claim 1, wherein said signal comprises a lightwave.7. The method of amplifying a signal from a carbon nanotube device asrecited in claim 1, including: arranging an array of depressions on saidsubstrate; and placing a growth seed in at least one of saiddepressions.
 8. A method of amplifying a signal using a carbon nanotubeamplifier comprising: placing a carbon nanotube on a receivingsubstrate; arranging an array of conductive metallic portions on saidsubstrate; and arranging a carbon nanotube on at least one of said arrayof metallic portions on said substrate wherein an application of energyfrom at least one external source applied to said substrate is effectiveto produce a signal from said amplifier having sum and differencecomponents.
 9. A method of using a carbon nanotube assembly, comprising:arranging a signal responsive array of nanotubes on a substrate;heterodyning a signal processed by said array of nanotubes on saidsubstrate.
 10. The method as recited in claim 9, wherein saidheterodyning said signal processed by said array of nanotubes comprisesoutputting a sum or product of said signal processed.
 11. The method asrecited in claim 9, wherein said signal processed is amplified by saidcarbon nanotube assembly.
 12. The method as recited in claim 9, whereinsaid signal processed comprises a lightwave.